Selected image acquisition technique to optimize patient model construction

ABSTRACT

A system and a method are disclosed that allow for generation of a model or reconstruction of a model of a subject based upon acquired image data. The image data can be acquired in a substantially mobile system that can be moved relative to a subject to allow for image acquisition from a plurality of orientations relative to the subject. The plurality of orientations can include a first and final orientation and a predetermined path along which an image data collector or detector can move to acquire an appropriate image data set to allow for the model of construction.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/908,195 filed on Oct. 20, 2010. The disclosure of the aboveapplication is incorporated herein by reference.

FIELD

The present disclosure relates to imaging a subject, and particularly todetermining and performing an optimal movement of an imaging devicerelative to the subject and constructing a model of the subject.

BACKGROUND

This section provides background information related to the presentdisclosure which is not necessarily prior art.

A subject, such as a human patient, may select or be required to undergoa surgical procedure to correct or augment an anatomy of the patient.The augmentation of the anatomy can include various procedures, such asmovement or augmentation of bone, insertion of implantable devices, orother appropriate procedures. A surgeon can perform the procedure on thesubject with images of the patient that can be acquired using imagingsystems such as a magnetic resonance imaging (MRI) system, computedtomography (CT) system, fluoroscopy (e.g. C-Arm imaging systems), orother appropriate imaging systems.

Images of a patient can assist a surgeon in performing a procedureincluding planning the procedure and performing the procedure. A surgeonmay select a two dimensional image or a three dimensional imagerepresentation of the patient. The images can assist the surgeon inperforming a procedure with a less invasive technique by allowing thesurgeon to view the anatomy of the patient without removing theoverlying tissue (including dermal and muscular tissue) when performinga procedure.

SUMMARY

This section provides a general summary of the disclosure, and is not acomprehensive disclosure of its full scope or all of its features.

According to various embodiments, a method of acquiring image data of asubject with an imaging system is disclosed including positioning animaging system relative to a region of interest, which can beencompassed by at least a portion of a human subject. The imaging systemcan include a detector to detect emitted energy, such as X-rays, from asource. The source and the detector can be provided generally oppositeor opposed to one another in a gantry. A rotor can be positioned in thegantry that moves the source and the detector within the gantry. Movingthe detector generally includes moving the source at a fixed positionrelative to the detector to maintain the opposed positioning.

The method can further include positioning the gantry in a predeterminedfirst orientation relative to the human subject based upon knownpossible movements of the gantry and a detector within the gantry toacquire a selected image data set of the human subject and moving atleast one of the gantry and the detector to a predetermined finalorientation relative to the human subject while acquiring image data ofthe human subject to acquire the selected image data set of the humansubject. A three-dimensional model of the portion of the human subjectregarding which the image data was acquired can be constructed based onthe image data and the three-dimensional model can be displayed. Theimage data acquired of the human subject with the imaging system caninclude two-dimensional projections of the subject. These projectionsare acquired by detection of X-rays from the source. Thethree-dimensional model can be a three-dimensional volumetric modelderived and/or generated from the acquired image data. Two dimensionalprojections can also be generated of the model which are line integralsof a three-dimensional object or model.

Further areas of applicability will become apparent from the descriptionprovided herein. The description and specific examples in this summaryare intended for purposes of illustration only and are not intended tolimit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only ofselected embodiments and not all possible implementations, and are notintended to limit the scope of the present disclosure.

FIG. 1 is an environmental view of an imaging system in an operatingtheatre;

FIG. 2 is a flowchart of a procedure for acquiring image data of asubject for rendering a model of the subject;

FIG. 3 is a flowchart showing an expanded portion of the flowchart inFIG. 2;

FIGS. 4A-4E illustrate possible movements of an imaging system; and

FIG. 5 is a flowchart showing an expanded portion of the flowchart inFIG. 2.

Corresponding reference numerals indicate corresponding parts throughoutthe several views of the drawings.

DETAILED DESCRIPTION

Example embodiments will now be described more fully with reference tothe accompanying drawings.

With reference to FIG. 1, in an operating theatre or operating room 10,a user, such as a surgeon 12, can perform a procedure on a patient 14.In performing the procedure, the user 12 can use an imaging system 16 toacquire image data of the patient 14 for performing a procedure. Theimage data acquired of the patient 14 can include two-dimension (2D)projections acquired with a X-ray imaging system, including thosedisclosed herein. It will be understood, however, that 2D forwardprojections of a volumetric model can also be generated, also asdisclosed herein.

A model can be generated using the acquired image data. The model can bea three-dimension (3D) volumetric model generated based on the acquiredimage data using various techniques, including algebraic iterativetechniques, also as discussed further herein. Displayed image data 18can be displayed on a display device 20. The displayed image data 18 canbe a 2D image, a 3D image, or a time changing four-dimension image. Thedisplayed image data 18 can also include the acquired image data, thegenerated image data, both, or a merging of both the types of imagedata.

It will be understood that the image data acquired of the patient 14 canbe acquired as 2D projections, for example with a X-ray imaging system.The 2D projections can then be used to reconstruct the 3D volumetricimage data of the patient 14. Also, theoretical or forward 2Dprojections can be generated from the 3D volumetric image data.Accordingly, it will be understood that image data can be either or bothof 2D projections or 3D volumetric models.

The display device 20 can be part of a processor system 22 that includesan input device 24, such as a keyboard, and one or more processors 26(the one or more processors can include multiple-processing coreprocessors, microprocessors, etc.) that can be incorporated with theprocessing system 22. A connection 28 can be provided between theprocessor 26 and the display device 20 for data communication to allowdriving the display device 20 to illustrate the image data 18.

The imaging system 16 can include an O-Arm® imaging system sold byMedtronic Navigation, Inc. having a place of business in Louisville,Colo., USA. The imaging system 16, including the O-Arm® imaging system,or other appropriate imaging systems in use during a selected procedureare also described in U.S. patent application Ser. No. 12/465,206 filedon May 13, 2009, incorporated herein by reference.

The O-Arm® imaging system 16 includes a mobile cart 30 that includes acontrol panel or system 32 and an imaging gantry 34 in which ispositioned a source unit 36 and a detector 38. The mobile cart 30 can bemoved from one operating theater or room to another and the gantry 34can move relative to the cart 30, as discussed further herein. Thisallows the imaging system 16 to be mobile allowing it to be used inmultiple locations and with multiple procedures without requiring acapital expenditure or space dedicated to a fixed imaging system.

The source unit 36 can emit x-rays through the patient 14 to be detectedby the detector 38. As is understood by one skilled in the art, thex-rays emitted by the source 36 can be emitted in a cone and detected bythe detector 38. The source/detector unit 36/38 is generallydiametrically opposed within the gantry 34. The detector 38 can moverotationally in a 360° motion around the patient 14 generally in thedirections of arrow 39 within the gantry 34 with the source 36 remaininggenerally 180° from and opposed to the detector 38. Also, the gantry 34can isometrically sway or swing (herein also referred to as iso-sway)generally in the direction of arrow 40, relative to the subject 14,which can be placed on a patient support or table 15. The gantry 34 canalso tilt relative to the patient 14 illustrated by arrows 42, movelongitudinally along the line 44 relative to the patient 14 and the cart30, can move up and down generally along the line 46 relative to thecart 30 and transversely to the patient 14, and move perpendicularlygenerally in the direction of arrow 48 relative to the patient 14 toallow for positioning of the source/detector 36/38 relative to thepatient 14. The O-Arm® imaging device 16 can be precisely controlled tomove the source/detector 36/38 relative to the patient 14 to generateprecise image data of the patient 14. The imaging device 16 can beconnected with the processor 26 via connection 50 which can include awired or wireless connection or physical media transfer from the imagingsystem 16 to the processor 26. Thus, image data collected with theimaging system 16 can be transferred to the processing system 22 fornavigation, display, reconstruction, etc.

Briefly, according to various embodiments, the imaging system 16 can beused with an unnavigated or navigated procedure. In a navigatedprocedure, a localizer, including either or both of an optical localizer60 and an electromagnetic localizer 62 can be used to generate a fieldor receive or send a signal within a navigation domain relative to thepatient 14. The navigated space or navigational domain relative to thepatient 14 can be registered to the image data 18 to allow registrationof a navigation space defined within the navigational domain and animage space defined by the image data 18. A patient tracker or dynamicreference frame 64 can be connected to the patient 14 to allow for adynamic registration and maintenance of registration of the patient 14to the image data 18.

An instrument 66 can then be tracked relative to the patient 14 to allowfor a navigated procedure. The instrument 66 can include an opticaltracking device 68 and/or an electromagnetic tracking device 70 to allowfor tracking of the instrument 66 with either or both of the opticallocalizer 60 or the electromagnetic localizer 62. The instrument 66 caninclude a communication line 72 with a navigation interface device 74 ascan the electromagnetic localizer 62 and/or the optical localizer 60.Using the communication lines 74, 78 respectively, the probe interface74 can then communicate with the processor 26 with a communication line80. It will be understood that any of the communication lines 28, 50,76, 78, or 80 can be wired, wireless, physical media transmission ormovement, or any other appropriate communication. Nevertheless, theappropriate communication systems can be provided with the respectivelocalizers to allow for tracking of the instrument 66 relative to thepatient 14 to allow for illustration of the tracked location of theinstrument 66 relative to the image data 18 for performing a procedure.

It will be understood that the instrument 66 can be an interventionalinstrument and/or an implant. Implants can include a ventricular orvascular stent, a spinal implant, neurological stent or the like. Theinstrument 66 can be an interventional instrument such as a deep brainor neurological stimulator, an ablation device, or other appropriateinstrument. Tracking the instrument 66 allows for viewing theinstrument's 66 location relative to the patient 14 with use of theregistered image data 18 and without direct viewing of the instrument 66within the patient 14.

Further, the imaging system 16 can include a tracking device, such as anoptical tracking device 82 or an electromagnetic tracking device 84 tobe tracked with a respective optical localizer 60 or electromagneticlocalizer 62. The tracking device can be associated directly with thesource 36, the detector 38, the gantry 34, or other appropriate part ofthe imaging system 16 to determine the location or position of thedetector relative to a selected reference frame. As illustrated, thetracking device can be positioned on the exterior of the housing of thegantry 36. Accordingly, the imaging device 16 can be tracked relative tothe patient 14 as can the instrument 66 to allow for initialregistration, automatic registration or continued registration of thepatient 14 relative to the image data 18. Registration and navigatedprocedures are discussed in the above incorporated U.S. patentapplication Ser. No. 12/465,206.

With reference to FIG. 2, a flowchart 100 illustrates an exemplaryprocedure of acquiring image data with the imaging system 16 andperforming a procedure with the acquired image data and a selectedreconstruction and verifying/confirming/determining a success of theselected procedure. The flowchart 100 can begin in start block 102 andproceed to select a region of an anatomy of a subject to be imaged inblock 104. Selecting the appropriate region of the subject can includeselecting a region of the patient 14 for imaging. For example, if aspinal implant is to be positioned in a lumbar region, then selecting alumbar region of the patient to be imaged can be made. Similarly, if abrain or neuro procedure is to be performed, the brain or the head of apatient 14 can be imaged. In like manner a pelvis, legs, or any otherappropriate portion of an anatomy of the subject 14 can be imaged.

Once the region is selected, the region can be inputted in block 106.After inputting the region, an optimal movement of the imaging system 16can be automatically determined and/or recalled in block 108. Movementof the imaging system 16 can include movement of the source 36 and thedetector 38 generally 360° around a longitudinal axis 14L of the patient14 and movement of the gantry 34 relative to the patient 14, includingthe isometric sway angular movement 40, tilt movement 42, longitudinalmovement 44, and other movements of the gantry 34 relative to thepatient 14. Movement of the detector 38 alone or with movement of thegantry 34 can move the detector 38 and the source 36 relative to thepatient 14 to acquire image data at a plurality of selected locationsand orientations relative to the subject 14.

The optimal movement can be based on acquiring adequate image data togenerate an initial three dimension model in block 112. The model can begenerated, as discussed below, with the image data acquired duringmovement of the imaging system along the optimal path. The optimal pathcan be one that allows an appropriate image data collection with minimalradiation usage or exposure. The image data collection can be optimizedto acquire image data with minimal, but appropriate overlap of datacollection. Also, the optimization can allow for the collection ofsequential/step image collection or continuous image collection duringthe image data collection. Regardless, the optimal path is automaticallyexecuted by the imaging system to collect the appropriate amount ofimage data during the path.

Also, the optimal path can differ from a manual path in acquiring imagedata at only predetermined locations of the detector relative to thepatient 14. This will allow for the usage of only minimal radiationdosages to acquire the image data by collecting minimal, but appropriateamounts of image data of the patient. The path can be designed to movein non-circular motions relative to the patient 14 to achieve the imagedata collection and at selected times during the path from a beginningor initial position to a final position.

After automatically determining optimal movement in block 108, theimaging system 16 can be moved according to the optimal movement inblock 110. Image data can be acquired of the patient 14 while moving thesource/detector 36/38 which can be used, such as with transfer to theprocessor 26 or stored in any appropriate storage media, for analysisand reconstruction. Automatic reconstruction of an initial threedimensional model of the subject can be then be performed in block 112.Reconstruction of the three dimensional model can be performed in anyappropriate manner, such as using an algebraic techniques foroptimization.

Appropriate algebraic techniques include Expectation maximization (EM),Ordered Subsets EM (OS-EM), Simultaneous Algebraic ReconstructionTechnique (SART) and total variation minimization, as generallyunderstood by those skilled in the art. The application to performing a3D volumetric reconstruction based on the 2D projections allows forefficient and complete volumetric reconstruction. Generally, analgebraic technique can include an iterative process to perform areconstruction of the patient 14 for display as the image data 18. Forexample, a pure or theoretical image data projection, such as thosebased on or generated from an atlas or stylized model of a “theoretical”patient, can be iteratively changed until the theoretical projectionimages match the acquired 2D projection image data of the patient 14.Then, the stylized model can be appropriately altered as the 3Dvolumetric reconstruction model of the acquired 2D projection image dataof the selected patient 14 and can be used in a surgical intervention,such as navigation, diagnosis, or planning. The theoretical model can beassociated with theoretical image data to construct the theoreticalmodel. In this way, the model or the image data 18 can be built basedupon image data acquired of the patient 14 with the imaging device 16.

The 2D projection image data can be acquired by substantially annular or360° orientation movement of the source/detector 36/38 around thepatient 14 due to positioning of the source/detector 36/38 moving aroundthe patient 14 in the optimal movement. Also, due to movements of thegantry 34, the detector need never move in a pure circle, but rather canmove in a spiral helix, or other rotary movement about or relative tothe patient 14. Also, the path can be substantially non-symmetricaland/or non-linear based on movements of the imaging system 16, includingthe gantry 34 and the detector 38 together. In other words, the pathneed not be continuous in that the detector 38 and the gantry 34 canstop, move back the direction from which it just came (e.g. oscillate),etc. in following the optimal path. Thus, the detector 38 need nevertravel a full 360° around the patient 14 as the gantry 34 may tilt orotherwise move and the detector 38 may stop and move back in thedirection it has already passed.

The reconstructed model can then be displayed on the display device 20in block 114. As discussed above, the imaging system 16 can be used togenerate image data or allow for reconstruction of a model of thepatient 14 or portion of the patient 14 relating to the selected regionin block 104 substantially in the operating theatre 10. Accordingly, theimaging device 16 can be used immediately prior to or during anoperative procedure. Also, the imaging device 16 can be moved from oneoperating theater to another with the cart 30 that has wheels or isotherwise mobile. This can reduce requirements of operating roomsdedicated to imaging or having a fixed imaging system.

Because the imaging system 16 can be used during or before a procedure,a decision block can be used to determine whether procedures are to beperformed in block 116. If no procedure is to be performed then NO pathcan be followed to end block 120. It will be understood that thedisplayed reconstructed model can be viewed by the user 12 or anyappropriate person or technician for analyzing the patient 14. Thereconstructed model can be used to for analysis, diagnosis or planningas appropriately selected. If a procedure is to be performed, a YES path122 can be followed to a second decision block 140 to determine whetherthe procedure is to be navigated.

If the procedure is to be navigated, a YES path 142 can be followed toregister the reconstructed model to an appropriate reference frame (suchas the dynamic reference frame 64) associated with the subject in block144. Registration can be performed in any appropriate manner such asidentifying landmarks or fiducials on the patient 14 and related marksin the image data 18. The registration can be substantially automatic,inherent by positioning the patient 14 at a known location relative tothe imaging device 16, or manually. Once registration is achieved,registration can be maintained with the dynamic reference frame 64connected to the patient 14 and tracked with the appropriate trackingsystem using the selected localizer 60, 62. Once registered, a procedurecan be navigable performed in block 146.

If it is selected to not perform a navigated procedure, then a NO path148 can be followed to perform a selected procedure without navigationin block 150. If no navigation is required, the localizer 60, 62 neednot be used to track instruments and the reconstructed image model canbe used to determine a particular procedure or for analysis in selectingan appropriate implant or the like.

Once the procedure has been performed, it can be selected to obtainconfirmation images in block 160. The confirmation images can be used toconfirm the procedure was completed satisfactorily, according to apredetermined plan, etc. The confirmation images can be equal in amount,less, or more than the image data acquired in block 110. After selectingto obtain confirmation images in block 160, discriminatory images can beobtained in block 162. The discriminatory images can be selected limitednumber of images of the patient 14 at discrete positions relative to thepatient 14.

After acquiring or obtaining the discriminatory images in block 162, anoptimal path for the imager for acquiring comparative images canautomatically be determined in block 164. A procedure of obtaining thediscriminatory images in block 162 and automatically determining anoptimal comparative imager path for comparative images in block 164 willbe described in further detail herein. Determining the optimalcomparative path can include avoiding regions of collision. This caninclude a user inputting or the system can recall positions ofpositioned instruments and avoid colliding with these in the optimalpath. The items that may cause collision need not necessarily besurgical instruments, but can be other items in the operating theater.Nevertheless, once the optimal comparative path for acquiring thecomparative images is determined, the imager can be moved along theoptimal comparative path in block 166 and comparative image data can beacquired during movement in the optimal comparative path in block 168.

An automatic reconstruction of a post procedure 3D reconstructed model,also referred to herein as a comparative model, using the comparativeimage data to compare to the initial reconstructed model can beperformed in block 170. The post procedure or comparative model is basedon image data, such as 2D projections, acquired of the patient 14 aftera portion of or all of the procedure has been performed. The comparativemodel can be reconstructed using a similar algebraic iterative techniquethat can be used to generate the new or the initial pre-procedure 3Dvolumetric reconstructed model based only on comparing the comparativeimage data to the initial three dimensional model, as discussed furtherherein. The comparative model can then be displayed on an appropriatedisplay device, including the display device 20, in block 172 and theprocedure can then end in block 120.

Thus, it will be understood that the flowchart 100 can be used fordifferent or multiple procedures including automatically determining anoptimal path for an initial patient image acquisition and modelreconstruction that can end in block 120. However, it can also bedetermined to perform a procedure and allow for navigation of aprocedure with the initial reconstructed model from block 112. Theprocedure can be navigated or not navigated and after the procedure, aconfirmation or verification can be performed using comparative imagedata acquired with the imaging device 16 to image the patient 14 to viewthe results of the performed procedure. The method can then end in block120 after performing the procedure and performing a comparison orgenerating a comparative model with the image data.

The flowchart 100 illustrates a procedure or method that can begin withacquiring images of a patient, reconstructing a model of the patient,performing a procedure, and confirming or verifying a procedure withadditional imaging. As discussed above, automatically determining anoptimal movement of the imager in block 108 can include various steps orprocedures. As illustrated in FIG. 3 in a flowchart 200 of a method,procedures for determining the optimal movement of the imager in block108 are illustrated in the flowchart 200. The flowchart 200 can beunderstood to be an expansion of blocks 108 and 110 in flowchart 100.Accordingly, block 106, which includes inputting the selected region,can begin the method 200. Then the method 200 can end by flowing intoblock 112 to reconstruct the initial three dimensional model of thesubject 14. Accordingly, the flowchart 200 can be understood to be apart of the flowchart 100 expanded and illustrated in detail.

Once the region is selected in block 106, the flowchart 200 can beginwith block 202 by calling an optimal path from a memory device based onthe input region. Calling the optimal path can include accessing amemory system that can be included in the cart 30, associated with aprocessor 26, or at any other appropriate location. The optimal path 202can be based upon preacquired or predetermined knowledge of general orstandard anatomy of the subject, such as a human patient, the geometryof the imaging system 16, the possible movements of the imaging system16, and other criteria to obtain a selected or optimal image data of thesubject 14 based upon the input region in block 106. For example, theoptimal path can include an appropriate beginning or initial location ofthe detector 38 relative to the patient 38, movements of the detector 38and the gantry 34 relative to the patient 14, and a final location ofthe detector 38 relative to the patient 14. The path can be to achievean appropriate image data collection to allow for the initial threedimension reconstruction in block 112 of the selected region of thepatient 14.

The optimal path can be based upon testing and analysis of image dataacquisition of the patient 14 or patients prior to a current patient 14.The analysis can be based upon test image data acquired of variouspatients and a plurality of patients. Statistical and other analysis canthen be applied to the image data to determine optimal location forpositioning the detector 38 relative to the patient to image as theselected region. A path of movement of the detector 38 can then bedetermined within the movement range of the imaging device to acquirethe optimal image data at the determined locations. Generally, theoptimal path will allow for the acquisition of an appropriate amount ofimage data to allow for a true or appropriate three dimensionalreconstruction of the patient 14 with minimal exposure to radiation fromthe source 36. Regardless of the method for determining the optimalpath, the optimal path can be called in block 202 to determine or inputmovements of the imaging system 16 relative to the patient 14.

The optimal path can be used to acquire enough image data to form orreconstruct the initial three-dimensional image model of the patient 14in block 112, but with limited patient exposure to radiation or imageacquisition time. The optimal path will include both a path of movementand a timing and number of image data positions to be acquired. Thus,the detector 38 can be instructed to move relative to the patient 14 inthe selected path and either stop to acquire image data or collect imagedata at a selected rate.

The optimal path will, therefore, acquire an appropriate amount of imagedata with substantially only a necessary overlap of image positions thatallows for the model reconstruction. This can limit radiation exposureand eliminate manual movement of the imaging system, either with acontroller or with physical power, to acquire the image data. Theoptimal path in acquiring the image data for reconstruction can be usedto ensure that enough image data perspectives of the patient 14 areacquired for the reconstruction with minimal undersampling orunnecessary over sampling of different perspectives. Also, the movementof the imaging system in combination with the optimal path can ensurethat the detector 38 is able to reach all of the optimal imagingpositions.

The patient 14 can be positioned at a selected location relative to theimaging system in block 204, this position can be based on the calledoptimal path form block 202. Positioning the patient 14 relative to theimaging system 16 can include positioning the patient on the operatingbed or support 15 and can further include securing the patient withsecuring straps or members 208 to the patient support 15. Further,positioning the patient 14 relative to the selected imaging system 16can include positioning the patient 14 at a selected position relativeto the gantry 34 so that the input selected region from block 106 ispositioned at a selected position relative to the cart 30 or otherposition of reference for the imaging system. The gantry 34 is able tomove due to the mechanical connections to the gantry 34 to the cart 30relative to the cart 30 and the optimal path can be referenced to areference point of the cart 30. Thus, the patient 14 or other subjectcan be positioned relative to the reference position of the cart 30 sothat the optimal path can be achieved relative to the referenceposition. For example, if a lumbar region is to be imaged the patientcan be positioned such that the L1 vertebra is aligned with a referencepoint of the cart 30 and about 15 cm from the reference point. It willbe understood that the reconstruction can occur with selected amounts ofinterpolation based on small differences in varying patient anatomy andpositioning of the patient 14.

Additionally, the detector 38 is positioned on a rail or track systemwithin the gantry 34 and is able to rotate around a center definedrelative to the annular gantry 34 and therefore the detector 38 alsomoves relative to the cart 30. Accordingly, the patient 14 is moved to aposition relative to the imaging system 16, including the cart 30, whichallows the detector 38 to be positioned at a selected position relativeto the patient 14 to allow for acquisition of image data according tothe optimal path called in block 202. Again, the patient 14 can be movedrelative to a reference point relative to which the optimal path isselected and the detector 38 can be instructed to follow the optimalpath once the patient 14 is positioned in the selected position in block204.

Once the patient 14 is positioned in the selected location relative tothe imaging system in block 204, the gantry 34 can be moved to a startposition in block 206 and the detector 38 can be moved to a startposition in block 208. It will be understood that the imaging system 16may have a park or stationary orientation that may include a standard orset start position that does not require the gantry 34 or the detector38 to move to a specific start position for each optimal path, butinstead is a standard imaging system start position. Nevertheless, theoptimal path may include a selected optimal start position, which can beachieved by moving the gantry 34 to a start position in block 206 andmoving the detector 38 to a start position in block 208.

Further, it will be understood that moving the detector 38 also includesmoving the source 36, which is substantially diametrically opposed tothe detector 38 across the patient 14 and the gantry 34. As discussedabove, and understood by one skilled in the art, the source 36 can be anx-ray source. The detector 38 is generally positioned directly opposedto the source 36 on an opposite side of the subject to be imaged, suchas the patient 14. Discussion herein of movement of the detector 38,therefore generally, includes inherent movement of the source 36 toensure that a beam of x-rays passes through the patient 14 in anappropriate manner to be detected by the detector 38.

After the gantry 34 and the detector 38 are moved to the start positionin blocks 206, 208 respectively, block 210 can include detecting x-raysemitted from the source 36. As understood by one skilled in the art,once detection begins, image data acquisition also begins. Accordingly,if the detector 38 is positioned opposed to the source 36, with thepatient 14 in the beam of the x-rays, then image data is detected by thedetector of the patient 14. After the x-rays begin being emitted anddetected in block 210, decision block 212 allows for determining whatthe next movement is. If only a single image position is required ordetermined by the optimal path in block 202, then a none decision path214 can be followed. If the none decision path 214 is followed, then theprocessor can exit the flowchart 200 and move to the reconstructionblock 112 from the flowchart 100.

Generally, however, movement of the gantry 34 and/or the detector 38 maybe selected to achieve multiple orientations of the detector 38 relativeto the patient 14 to allow for a more complete or better reconstructionof a model of the patient 14. In particular, when reconstructing a threedimensional model it may be selected to acquire a plurality oforientations or positions of the detector 38 relative to the patient 14to allow for the three dimensional reconstruction. In particular, it maybe selected to move the detector 38 at least 360° around the patient 14to allow for detection of x-rays and therefore image data, at a complete360° circle around the patient 14 and therefore 360° around the regioninput in block 106. Although, movement of the detector 38 need not becircular, but can be spiral, etc., as discussed above.

The movement of the detector 38, however, may be generally stepwise orsequential or continuous and image data acquisition may also follow thisprocess. In other words, the detector 38 may be allowed to continuallyor substantially continually (e.g. about 10 millisecond detectorrefresh-rate) collect image data of the patient 14 as the detector movesin the optimal path. Alternatively, or in addition to the continuouscollection, the detector 38 may be moved from one optimal location toanother and only collect limited image data at the selected locations togenerate a more step-wise image data acquisition.

Accordingly, the decision block 212 of what the next movement is cangenerally lead to at least one of five movement choices. It will beunderstood that the imaging system 16 can move in any appropriate mannerand those discussed here are exemplary of movement of the O-Arm® imagingsystem. Regardless, a first type of movement can include rotationalmovement of the detector 38 around the patient in block 216. Asexemplarily illustrated in FIG. 4A, rotation of the detector 38 caninclude movements of the detector 38 generally in the direction of arrow39 in an annular or circular path around the gantry 34 of the imagingsystem 16. The patient 14 positioned within the imaging system 16 can beimaged with the x-rays by movement of the detector 38 relative to thepatient 14 as the detector moves in the annular path 39. Motorizedportions can move the detector 38 along the track within the gantry 34at precise steps or substantially continuous movements as selected bythe optimal path in block 202.

Selected movements can include perpendicular movement of the gantry 34in block 218 relative to the patient 14 and the cart 30 in the directionof arrow 48, as illustrated in FIG. 4A. The perpendicular movement ofthe gantry 34 allows the patient 14 to be positioned relative to thecart 30 on the patient support 15 with enough clearance for proceduresor other instruments. The gantry 34 can then move to a selected positionto move the detector 38 in the selected path, as discussed herein.

The gantry 34 can also be tilted, as illustrated in FIG. 4B relative tothe patient 14 or the cart 30 generally in the direction of arrow 42 inblock 220. Tilting of the gantry 34 allows for tilting of the beam ofx-rays, illustrated by vector XV1 from a first position illustrated by avector XV1 to a second position or orientation illustrated by a vectorXV1′ and the second orientation of the detector 38 a in the tiltedgantry 34 a. Accordingly, the gantry 34 can tilt relative to the patient14 to provide a selected orientation of the detector 38 relative to thepatient 14. It will be understood that the gantry 34 can tilt eitherduring or at a selected time in the path of the detector or movement ofthe detector 38 relative to the patient 14. Accordingly, the detectormay move from a start position, as illustrated in FIG. 4A to a positionapproximately 90° rotated relative to the patient 14 and then the gantry34 can tilt relative to the patient 14 and the detector 38 can eitherreturn the same 90°, move an additional arc in the same direction aspreviously moved, or return a portion of the arc previously traversed.It will be further understood that the detector 38 may rotate an entire360° within the gantry 34 and then the gantry 34 can tilt and thedetector 38 can return or move in a reverse direction within the gantrytowards its initial starting position within the gantry, but along adifferent path defined now by the tilted gantry 34 relative to thepatient 14.

The gantry 34 can also translate longitudinally in block 230 asillustrated in FIG. 4C. The translation can generally be in thedirection of arrow 44, as also illustrated in FIG. 1, which cangenerally be along the longitudinal axis of the patient 14L. Again,movement of the gantry 34 can be used to move the detector 38 from afirst position or a selected position to a second selected positionillustrated in phantom 38 b. Thus, the gantry 34 can move from a firstselected position 34 to a second selected position 34 b and subsequentlythe direction or orientation of the x-ray beam can move from a firstposition, illustrated by a vector XV2 to a second position illustratedby vector XV2′.

The gantry 34 can also iso-sway in block 240 as illustrated in FIG. 4D.The iso-sway of the gantry 34 can be generally in the direction of arrow40, as also illustrated in FIG. 1. Iso-swaying the gantry 34 moves thegantry 34 in a portion of an arc around a line tangent to the gantry 34.Iso-swaying the gantry 34 can move the detector 38 from a firstposition, illustrated as 38 in FIG. 4D to a second position illustratedin phantom 38 c in FIG. 4D. The iso-sway of the gantry 34 can allow fordifferent orientations of the detector 38 relative to the patient 14 notallowed only by tilting the gantry 34 in block 220 as illustrated inFIG. 4B. Accordingly, the gantry 34 can also be iso-swayed relative tothe patient 14 as illustrated in FIG. 4D to move the detector 38 and therespective x-ray vector relative to the patient 14.

Finally, the gantry can be translated up and down in block 250 asillustrated in FIG. 4E. Moving the gantry 34 up and down relative to thecart 30 or the patient 14 can move the detector 38 from a firstposition, illustrated as 38 in FIG. 4E to a second position, illustratedin phantom 38′ in FIG. 4E. Accordingly, the x-ray vector can move from afirst position XV4 to a second position XV4 as the gantry is moved to asecond position 34 d′. Although the movement illustrated in FIG. 4Eillustrates that the x-ray vector XV is generally still substantiallyperpendicular to a longitudinal axis of the patient 14, it will beunderstood that movement of the imaging system 16 can be combined.

Accordingly, movement of the gantry 34 up and down as illustrated ordefined by movement in the direction of arrow 46 can be combined withiso-swaying in block 240 and tilting in block 220 to move the x-rayvector or beam vector relative to the patient 14 that is not allowed bysimply tilting or isotilting the gantry 34. The coordinated movements ofthe gantry 34 and the detector 38 can cause longitudinal pivoting andother coordinated movements relative to the patient 14. The coordinatedmovements allow the gantry 34 and the detector 38 to move substantiallysimultaneously or effectively simultaneously to achieve movement inmultiple axes during a movement relative to the patient 14.

Once the next movement is determined the movement can be achieved in oneof the blocks 216, 218, 220, 230, 240, or 250. After the appropriatemovement is determined or made in one of the respective movement blocks,a further decision block can be used to determine whether anothermovement is required in block 260. If no additional movement isrequired, then a NO path 262 can be followed to the reconstruction block112 and follow the flowchart 100 discussed above.

It will be understood that certain optimal paths may only require asingle movement from an original or starting position to achieve aselected data set acquisition. Further, it will be understood thattranslating a detector 216 can include a continuous translation or caninclude a certain amount of translation. Accordingly, if the movementselected in block 212 is translation of the detector 38, a single 360degree sweep or scan can be made of the patient 14 and that can be theonly movement required to acquire the image data or reconstruction inblock 112.

Nevertheless, additional movements may be required, such as combinationof different movements, therefore a YES path 264 can be followed back tothe initial decision block 212 to determine what the next movement is.The next movement can be included in the optimal path called in block202 and can include additional movements, such as a selected tilt ortranslation or can include moving the gantry 34 after translating thedetector 38 a selected amount. For example, as discussed above, thedetector 38 can translate a certain arc length, such as about 90°, andthen the gantry 34 can be tilted in block 220 a selected amount, such asabout 5° from its last position, thus allowing the detector 38 totranslate at a different orientation relative to the patient 14.Accordingly, the determination of whether another movement is requiredin block 260 can be used to move the detector 38 and substantiallycomplex orientations and movements relative to the patient 14 to acquirean optimal image data set according to the optimal path in block 202.

The imaging system can move relative to the patient 14 in a selectedamount which can be used to identify or determine the optimal path whichcan be called in block 202. Movement of the imaging system 16 caninclude a substantially 360° rotation or translation of the detector 38relative to the patient 14. Additionally, tilt movement of the gantry 34can be about 30 degrees)(°) to about 60°, including about 40° to about50°, and further including about 45° either direction of a line normalto the longitudinal axis 14L of the patient. The gantry 34 can also havea total longitudinal translation movement of about 10 centimeters (cm)to about 30 cm, including about 15 cm to about 20 cm, and includingabout 17.8 cm. The gantry 34 can have an isotilt of about 5° to about20°, and further about 10° to about 15° and further about 12° eitherdirection of a line substantially normal to the longitude axis 14L ofthe patient 14. Finally, the gantry 34 can have a total up and downmovement of about 20 cm to about 70 cm, about 40 cm to about 50 cm, andfurther about 45.7 cm.

Any of the possible movements can be combined to move the detector 38 atany selected position relative to the patient 14 required by the optimalpath. The optimal path called in block 202, however, can be based uponthe region inputted in block 106 and can be substantially standardizedfor a selected type of subject, such as a human patient. Thus, theoptimal path can be standardized based on analysis, image data acquiredat various positions of the detector, etc. for a human patient. Forexample, to allow for a reconstruction of a vertebra the optimal pathcan include obtaining two orthogonal images in a first plane, tiltingthe gantry 34 collecting two additional orthogonal images at differentlocations, then isotilting the gantry 34 and repeating. The movements ofthe imaging system 16 can be used to ensure an appropriate perspectiverelative to the patient 14 and the optimal path can be used to ensurethat the optimal number of image data locations are acquired for eachpatient.

The optimal path, in accessing it for acquiring the image data, can beused to limit radiation and power usage to only a minimal or optimalamount for image data collection. Further, a technician or user of theimaging system 16 need not guess or determine positions for image dataacquisition for each new patient. This can reduce procedure time andtraining. In other words, a completely manual system may require theuser to ensure positioning of the patient 14 relative to the detector 38is proper for each image and can overcompensate for limitations inknowledge of the imaging system 16 by over acquiring the image data and,thus, possibly using more power and radiation than necessary. Also, theoptimal path can ensure that enough image data is acquired for the modelreconstruction with a minimal number of image data acquisition positionsor radiation usage. Thus, over- or under-sampling can be avoided.

The optimal path can be stored and accessed substantially quickly duringa procedure to allow for the acquisition of an image data setsubstantially immediately prior to the performing of a procedure for theparticular type of subject, such as the human patient 14. It will beunderstood, that substantially immediately prior to performing of aprocedure can include the time after the operating theater 12 has beenprepared for the procedure and the patient 14 is also prepared for theprocedure and either the operating surgeon is in the operating theatre12 or preparing to enter the operating theater 12. Thus, the image dataacquired of the patient 14 is substantially immediately beforeperforming the procedure and generally in the same room or operatingtheater.

The flow chart 100 illustrated in FIG. 2, as briefly discussed above,illustrates a method for automatically acquiring image data, forming aninitial reconstruction or model of the patient, performing a procedure,and performing the confirmation or verification procedure. Theconfirmation or verification procedure discussed above in flow chart 100is illustrated in greater detail in flow chart 300 in FIG. 5. It will beunderstood that the procedure illustrated in flow chart 300 can beincluded in the flow chart 100 discussed above. It is described ingreater detail here for understanding of a confirmation or verificationprocedure according to various embodiments.

After performing a selected procedure, it can be selected to obtainconfirmation or verification images for a comparative reconstruction inblock 160. Once this selection has been made to obtain verificationimages or to reconstruct the verification or comparative model, an inputof the procedure type or location can be made in block 302. The input ofthe location or type of procedure in block 302 can be manually input bythe user 12 after performing the procedure or could be called orrecalled from the region initially selected in block 104, or determinedby performing a navigated procedure in block 146. It will be understoodthat the navigated procedure can include inputs regarding the type ofimplant, region of the anatomy of the patient 14, or other informationthat can be used to determine the type or location of the procedure forinput in block 302. Accordingly, the input of procedure type or locationin block 302 can be manually input at a selected time by the user 12, orany other appropriate individual, or can be automatically determined orrecalled based upon previous inputs.

With or without the procedure or location input in block 302, adetermination of possible locations of change or augmentation to thesubject 14 can be made in block 304. The determination of possiblelocation are subject to change or augmentation in block 304 can be basedupon known movement of the patient 14 based upon the procedure performedin block 146 or 150, or can be input by the user 12 or other appropriateindividual manually. For example, if the procedure is to implant aspinal implant, it may be known which vertebrae were affected and whichvertebrae should be imaged for a comparative reconstruction. Thisdetermination can be made automatically by the processor 26, or otherappropriate processor executing instructions based upon the inputprocedure, or based upon a manual input by the user 12 or otherappropriate individual.

Also, if the procedure is a navigated procedure the processor caninclude input regarding the portion of the patient 14 on which aprocedure is performed and/or which areas or volume of the initial modelmay be changed due to the tracked instrument relative to the registeredimage data. The patient 14 can be registered to the image data 18displayed on the display 20. The image data 18 can include the initial3D reconstructed model. Thus, the initial 3D model can be registered tothe patient 14 and the location of the instrument 66 is tracked relativeto the patient 14 and the image data 18. This, in turn, allows theprocessor system 26 to determine the location of the instrument 66,possible change of the patient 14, etc. This can be used as an input inblock 304 to assist in determining an optimal comparative path in block312. Additionally, geometry, anatomical effect, etc. of an implant orinstrument can also be input or known to assist in determining possibleareas of change in the patient 14.

Further, determining a possible location of subject change oraugmentation can include both the direct portion of the anatomy affectedby the procedure, such as the vertebrae to which an implant is attachedor positioned, and also other anatomy that may be affected due to theprocedure. For example, if a spinal implant is to re-position onevertebra relative to another vertebra, the other soft tissue orvertebrae beyond the ones directly implanted or connected with animplant may be affected due to movement of the anatomy of the patient14. Accordingly, the determination of the location of subject change oraugmentation can include both the direct area of a procedure andsurrounding areas or other areas of the subject anatomy based upondetermination of the user 12, previous inputs into the system, and otherstored data.

Once the determination of subject change or augmentation has been made,acquisition of discriminatory image data can be acquired atdiscriminatory locations near the possible locations of change oraugmentation in bock 306. The discriminatory images or image data can bediscrete images that are acquired at spaced apart locations relative tothe patient 14. As discussed above, the detector 38 can move relative tothe patient according to the possible movements of the imaging system16. However, to form a comparative reconstruction model, it can beselected to only image those portions of the patient 14 that havechanged due to the procedure. Accordingly, the discriminatory images canbe made relative to the patient 14 at discrete locations to determinethose areas that should be imaged to allow for the reconstruction of thecomparative model. The discrete images can include a small number ofimages, such as one, two, three or ten or any appropriate number ofimages that can be less than an entire number of images or discretelocations of the detector 38 required to form the initial or thecomparative reconstructed model.

Once the discriminatory image data is acquired at the discrete locationsof block 306, it can be compared to the initial three dimensional modelreconstruction in block 308. For example, the discriminatory image datacan be 2D projections that are acquired of the patient at selectedlocations. These can be compared to forward projections or theoreticalprojections from the initial 3D reconstructed model of the patient 14 atidentical or substantially identical locations. Thus, the discriminatoryimage data acquired at a position relative to the patient 14 can becompared to substantially the identical forward projected position, evenif one or more of the initial projections was not taken at the sameposition relative to the patient 14 as one or more of the discriminatoryimage projections. Also, the discriminatory images can be selected to bein substantially identical locations to at least some of the image datacollection locations in block 110 so that the discriminatory images canbe compared directly to the first images from block 110.

From the comparison, a determination of whether a change has occurred inthe discriminatory image data greater than a threshold amount from theinitial reconstructed model can be made. The threshold can be set at anyappropriate level and can be selected for imaging speed, reconstructionspeed, image acquisition or radiation dose, etc. Generally, however, thethreshold will be used to determine if a discriminatory image isdifferent from the initial model. The difference can be a statisticaldifference or percentage difference or variance in a pixel or voxel data(e.g. brightness, contrast, etc.). Thus, it will be understood, that thethreshold need not be a set value for a particular image.

The comparison made in block 308 can assist in determining whether anydiscrete location at which discriminatory image data was acquired inblock 306 includes differences from the initial reconstructed model. Adetermination of subject areas of change from the initial modelreconstruction based on the discriminatory image data can then be madein block 310. The determination of subject areas of change in block 310is based upon the comparison in block 308. For example, if a firstdiscrete location at which a first discriminatory image data is acquiredshows no or substantially no change (i.e. below the threshold level),then a determination of subject area of change can be determined to nothave occurred at the first discrete location. It will be understood thatthe amount of change (e.g. the threshold) can be set at a particularthreshold such as about 0.1% to about 10%, including about 2%, andfurther including about 1% change of the discriminatory image datacompared to a projection based on the initial model. The amount ofchange can be based upon movement of portions of the anatomy orinclusion of implants, volume of anatomy in the area, or otherappropriate thresholds. A determination can be made in block 310 if achange requiring additional images is found in the discriminatoryimages, that being that the amount of change found in the comparisonshows an amount of change above the threshold.

After the determination of subject areas of change is made in block 310,a determination of an optimal comparative path to image the subject areaof change can be made in block 312. The determination of an optimal pathcan be based upon the determined areas of subject change in block 310.For example, if ten discriminatory images are taken in block 306 and adetermination that areas 3, 4, 5 and 6 show a change above thethreshold, then the determination of an optimal comparative path can bemade to image the area encompassing the discrete areas 3-6 of the totalten discriminatory images taken. Accordingly, the optimal path can bedetermined to be less than the automatically determined optimal path inblock 108. If the comparative path is shorter or includes fewer acquiredprojections then the amount of radiation, time, movement, etc. needed toacquire the comparative images is generally less than to acquire theinitial image data. It will be understood, however, that if the amountof change is great enough (e.g. a major reconstruction of the patient's14 anatomy has occurred) then the determined optimal comparative path inblock 312 can be substantially equal to or the same as the optimal pathdetermined in block 108.

The determined optimal comparative path, however, can be based upon thespecific location of a procedure and the amount of possible change doneto the patient 14 during the procedure. The determined optimalcomparative path can also include or account for knowledge orinformation regarding the procedure or implant positioned in the patient14. For example, if a spinal disc implant is positioned in the patientor if a spinal fusion occurs, the geometry of the implant is known. Thegeometry of the implant can be used in determining an appropriatecomparative path for acquiring comparative image data. The geometry ofthe implant can help in determine the distance changes of the anatomybased on dimensions and affects of the implant, amount of change, volumeof the patient 14 affected, etc.

The discriminatory images acquired in block 306 can assist indetermining whether or where the change is great enough to require theacquisition of additional images for forming a comparative reconstructedmodel. The optimal comparative path can also include a plurality ofpaths. In other words, several passes over a similar or identicalportion of the patient 14 can be used to ensure appropriate sampling andappropriate orientation of the detector 38 relative to the patient 14for image data acquisition. Accordingly, the comparative reconstructedmodel, as discussed further herein, can be based upon the initialreconstructed model in block 112 augmented only to show the change tothe patient 14 due to the procedure and determined with the comparativeimage data.

Once the determined optimal comparative path is determined in block 312,the detector can be moved on the optimal comparative path in block 166.Comparative image data can then be acquired in block 168 as discussedabove. The comparative image data will be the image data acquired whilethe detector is moved on the optimal comparative path determined inblock 312. Again, the determined optimal comparative path can bedetermined substantially intra-operatively or substantially immediatelypost operatively based upon the discrete image data. Also, acquiring theimage data in block 168 can be substantially different for each andevery patient on which a procedure is performed based upon the amount ofchange, the type of implant used, the initial reconstructed model, andother parameters based on the specific patient 14 on which a procedureis being performed.

Once the comparative image data is acquired in block 168, a calling orrecalling of initial model reconstruction can be performed in block 320.The initial model reconstruction from block 112 can be stored in anappropriate memory system that is associated with the processor 26 orseparate from the processor 26, but can be recalled for comparing to thecomparative image data from block 168. The comparison of the comparativeimage data in block 168 to the called initial model reconstruction canbe performed in block 322. The comparative image data can be iterativelycompared to the initial model reconstruction in block 322 to allow for aformation of a comparative model.

The comparative model formed in block 322 can be generated based uponthe comparative image data and the initial model and can include lessprocessing than forming the initial model. The lower processing can bedue, at least in part, because the initial model should remain unchangedfor the areas of the patient 14 unaffected by the procedure. Also, theknown movement of the instruments 66 (i.e. from tracking theinstruments) and/or geometry of implants can be used to assist informing the comparative model. Thus, if the procedure, is not a drasticor overly invasive procedure the comparative reconstruction may requireonly processing of the areas of change of the patient 14. Although itwill be understood that the areas of change can be substantial such thatthe comparative model can be substantially different than the initialmodel from block 112. In other words, the comparative model may be basedsubstantially completely on a new image data set collected duringcollecting the comparative image data in block 168.

Also, acquiring the discrete images in block 306 and the comparativeimage data in block 168 can allow for the reduced x-ray exposure to thepatient 14 and the user 12 and other individuals in the operatingtheater 10 by allowing for the determination of a small area of change,if possible, rather than reimaging the entire area or volume of thepatient 14 used in block 112 to generate the initial reconstructedmodel. Accordingly, the radiation exposure of the patient 14 can beminimized based upon the procedure performed and the determined optimalcomparative path in block 312. Nevertheless, the comparative modeldetermined in block 322 can be used to verify or confirm the procedureperformed on the patient 14, including a selected result being achievedor solution to the ailment of the patient 14 with the procedure.

The comparative model can be displayed at 172. However, either prior toor after forming the comparative model, a determination can be made ofwhether the comparative model is beyond the threshold change differencefrom the discriminatory image data acquired in block 306 or the initialmodel called in block 320 in determination block 326. As discussedabove, the threshold can be a percentage change, an absolute amount, orother amount of change between the comparative model and the initialdetermined model in block 322 or compared to prior models or the imagedata. If no threshold change is determined, then a NO path 328 can befollowed to block 172. However, if an amount of change greater than athreshold amount is determined, then a YES path 330 can be followed toblock 312 to further determine an optimal path to acquire comparativeimage data. The amount of change or the threshold change can also referto variance in the image data acquired during the acquisition of thecomparative image data and comparative model generated or formed inblock 322.

Thus, the generation of the comparative model can be an iterativeprocess and allow the image data to be acquired in several steps.Accordingly, an initial optimal path can be determined in block 312 anda comparative image data model can be generated in block 322 based uponthe single path and acquisition of data. If an amount of variance orchange is determined between the comparative model and the initial modelor the discriminatory image data, however, a second optimal comparativepath can be determined to acquire additional image data at areasnecessary to remove variances from the comparative image model. Thereason for acquiring additional image data or selecting to acquireadditional image data can include sampling rates of selected areas,movement of the patient, change to the patient, or other factors inacquiring enough image data to generate an appropriate comparative imagedata model in block 322.

The foregoing description of the embodiments has been provided forpurposes of illustration and description. It is not intended to beexhaustive or to limit the invention. Individual elements or features ofa particular embodiment are generally not limited to that particularembodiment, but, where applicable, are interchangeable and can be usedin a selected embodiment, even if not specifically shown or described.The same may also be varied in many ways. Such variations are not to beregarded as a departure from the invention, and all such modificationsare intended to be included within the scope of the invention.

What is claimed is:
 1. A method of analyzing image data of a subjectwith an imaging system, comprising: acquiring initial image data of aselected portion of the subject from an imaging system positioned aroundthe subject; constructing a first three-dimensional model of theselected portion of the subject using the acquired image data; receivinginto a processor system an input regarding a procedure performed on aportion of the subject; acquiring discriminatory discrete location imagedata of the subject at locations limited to the portion of the subjecteffected by the inputted procedure; executing instructions with aprocessor to determine a comparative movement of a gantry and a detectorthat is less than the movement of the detector while acquiring theinitial image data of the subject that includes instructions for movingthe gantry and the detector to acquire the comparative image data;comparing the acquired discriminatory discrete location image data to atleast a portion of the constructed first three-dimensional model of theportion of the subject; identifying specific regions having a changebetween the acquired discriminatory discrete location image data and asimulated projection image data from the first constructedthree-dimensional model of the portion of the subject; acquiringadditional comparative image data of identified specific regions of athreshold change; and constructing a comparative model of the subjectafter the performed procedure; wherein acquiring the additionalcomparative image data includes acquiring less image data of the subjectthan with the acquired initial image data of the subject; whereinacquiring less image data includes exposing the subject to less x-rayradiation than while acquiring the initial image data of the subject;wherein constructing the comparative model of the subject after theperformed procedure includes changing the three-dimensional model withthe acquired additional comparative image data.
 2. The method of claim1, wherein the change is defined as a threshold change.
 3. The method ofclaim 2, wherein the threshold change is a percentage change.
 4. Themethod of claim 1, wherein acquiring the initial image data of thesubject, includes: positioning the gantry in a predetermined firstorientation relative to the subject based upon known possible movementsof the gantry and the detector within the gantry to acquire a selectedimage data set of the subject; and moving the gantry and the detector toa predetermined final orientation relative to the subject whileacquiring image data of the subject to acquire the selected image dataset of the subject.
 5. The method of claim 1, further comprising:positioning the gantry to completely annularly encompass at least aportion of the subject; wherein the imaging system includes the gantry.6. A method of analyzing image data of a subject with an imaging system,comprising: constructing a first three-dimensional model of a portion ofthe subject with an initial image data that has been acquired of thesubject; comparing an acquired discriminatory discrete location imagedata, wherein the discriminatory discrete location image data has afirst image acquired at least a first discrete location spaced apartfrom a second image acquired at a second discrete location, to at leasta portion of the constructed first three-dimensional model of theportion of the subject; identifying specific regions having a thresholdchange between the acquired discriminatory discrete location image dataand a simulated projection image data from the first constructedthree-dimensional model of the portion of the subject; determining,based at least on the identified specific regions having the thresholdchange, at least one location of a detector in a gantry to acquire acomparative image data regarding the specific regions having theidentified specific regions having the threshold change after a periodthat the acquired discriminatory discrete location image data isacquired; acquiring the comparative image data; and constructing acomparative model of a region of interest based on the identifiedspecific regions of change relative to the constructed firstthree-dimensional model including the acquired comparative image data.7. The method of claim 6, further comprising: acquiring the comparativeimage data with x-rays at the determined at least one location of thedetector; acquiring the initial image data with x-rays.
 8. The method ofclaim 6, further comprising: executing instructions with a processorsystem to determine at least one location of the detector to acquire thecomparative image data regarding the identified specific regions havingthe threshold change.
 9. The method of claim 8, further comprising:executing instructions with the processor system to determine aplurality of locations for positioning the detector to acquire aplurality of comparative image data regarding the identified specificregions having the threshold change.
 10. The method of claim 6, furthercomprising: acquiring the initial image data of the subject, including:positioning the detector in the gantry in a predetermined firstorientation relative to the subject based upon known possible movementsof the detector and the gantry to acquire a selected image data set ofthe subject; and moving the gantry and the detector to a predeterminedfinal orientation relative to the subject while acquiring image data ofthe subject to acquire the selected image data set of the subject. 11.The method of claim 6, further comprising: acquiring the comparativeimage data with x-rays at the determined at least one location of thedetector; and acquiring the initial image data with x-rays.
 12. Themethod of claim 11, further comprising: constructing a comparative modelof a region of interest based on the identified specific regions ofchange relative to the constructed initial three-dimensional modelincluding the acquired comparative image data.
 13. A method of analyzingimage data of a subject with an imaging system, comprising: constructinga first three-dimensional model of at least a portion of the subjectwith a first image data acquired with an imaging system; receiving aninput including at least a location of a procedure performed on aneffected portion of the subject; comparing an acquired limited number ofimages as discriminatory discrete location image data of the subject toat least a portion of the constructed first three-dimensional model ofthe portion of the subject, wherein the acquired limited number ofimages is based at least in part on the received input regarding thelocation of the procedure performed on the effected portion of thesubject; identifying specific regions having a change between theacquired discriminatory discrete location image data and a simulatedprojection image data from the first constructed three-dimensional modelof the portion of the subject; and constructing a secondthree-dimensional model as a comparative model of the subject based atleast on a comparative image data acquired after the identifyingspecific regions have change.
 14. The method of claim 13, wherein thelimited number of images is at locations limited to an effected portionof the subject based on the procedure; wherein the limited number ofimages includes a number of images less than a number of images in thefirst image data for constructing the first three-dimensional model. 15.The method of claim 14, further comprising: executing instructions witha processor to determine a comparative movement of the imaging systemthat is less than a movement of the imaging system while acquiring thefirst image data of the subject, wherein the instructions includemovement instructions for the imaging system to acquire a comparativeimage data of identified specific regions of a threshold change whichincludes acquiring less image data of the subject than the first imagedata of the subject.
 16. A method of analyzing image data of a subjectwith an imaging system, comprising: constructing a firstthree-dimensional model of at least a portion of the subject regardingwhich a first image data was acquired with an imaging system; comparingan acquired limited number of images as discriminatory discrete locationimage data of the subject to at least a portion of the constructed firstthree-dimensional model of the portion of the subject, wherein theacquired limited number of images is based on an input regarding aprocedure performed on an effected portion of the subject; identifyingspecific regions having a change between the acquired discriminatorydiscrete location image data and a simulated projection image data fromthe first constructed three-dimensional model of the portion of thesubject; acquiring a comparative image data of identified specificregions having the change, which includes acquiring less image data ofthe subject than the first image data of the subject; and constructing asecond three-dimensional model as a comparative model of the subjectbased at least on the comparative image data; wherein constructing thesecond three-dimensional model as the comparative model of the subjectincludes changing the first three-dimensional model with the acquiredcomparative image data.